I put a cavalier 2.4 in my grand am which had a 2.4 now it wont start
Check over all of your connections to all of the sensors and switches.
Did you check for spark, fuel pressure, and injector pulse? Did you install all of your body and computer grounds that connect to the engine block?
What was the mileage on the engine? What was the condition of the timing belt? Check engine compression, if the belt slipped a tooth you could have a hard start or no start condition.
You may want to try swapping the ECM with the engine it was matched up with. Sometimes the calibration from each car model can be different.
Try these few suggestions and get back to me when you can.